Thermosetting compositions containing epoxy functional polymers prepared by atom transfer radical polymerization

ABSTRACT

A thermosetting composition comprising a co-reactable solid, particulate mixture of (a) epoxy functional polymer, and (b) co-reactant having functional groups reactive with the epoxy groups of (a), e.g., dodecanedioic acid, is described. The epoxy functional polymer is prepared by atom transfer radical polymerization and has well defined polymer chain architecture and polydispersity index of less than 2.5. The thermosetting compositions of the present invention have utility as powder coatings compositions.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. ProvisionalApplication Ser. No. 60/098601, filed Aug. 31, 1998, which is herebyincorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to thermosetting compositions ofone or more epoxy functional polymers and one or more coreactants havingfunctional groups that are reactive with epoxides. The epoxy functionalpolymer is prepared by atom transfer radical polymerization, and haswell defined polymer chain structure, molecular weight and molecularweight distribution. The present invention also relates to methods ofcoating a substrate, substrates coated by such methods, and compositecoating compositions.

BACKGROUND OF THE INVENTION

[0003] Reducing the environmental impact of coatings compositions, inparticular that associated with emissions into the air of volatileorganics during their use, has been an area of ongoing investigation anddevelopment in recent years. Accordingly, interest in powder coatingshas been increasing due, in part, to their inherently low volatileorganic content (VOC), which significantly reduces air emissions duringthe application process. While both thermoplastic and thermoset powdercoatings compositions are commercially available, thermoset powdercoatings are typically more desirable because of their superior physicalproperties, e.g., hardness and solvent resistance.

[0004] Low VOC coatings are particularly desirable in the automotiveoriginal equipment manufacture (OEM) market, due to the relatively largevolume of coatings that are used. However, in addition to therequirement of low VOC levels, automotive manufactures have very strictperformance requirements of the coatings that are used. For example,automotive OEM clear top coats are typically required to have acombination of good exterior durability, acid etch and water spotresistance, and excellent gloss and appearance. While liquid top coats,in particular epoxy-acid cured liquid coatings, can provide suchproperties, they have the undesirable draw back of higher VOC levelsrelative to powder coatings, which have essentially zero VOC levels.

[0005] Epoxy based powder coatings, such as epoxy-acid powder coatings,are known and have been developed for use as automotive OEM clear topcoats. However, their use has been limited due to deficiencies in, forexample, flow, appearance and storage stability. Epoxy based powdercoating compositions typically comprise a co-reactant, e.g., acrosslinking agent, having functional groups that are reactive withepoxides, e.g., dodecanedioic acid, and an epoxy functional polymer,e.g., an acrylic copolymer prepared in part from glycidyl methacrylate.The epoxy functional polymers used in such epoxy based powder coatingscompositions are typically prepared by standard, i.e., non-living,radical polymerization methods, which provide little control overmolecular weight, molecular weight distribution and polymer chainstructure.

[0006] The physical properties, e.g., glass transition temperature (Tg)and melt viscosity, of a given polymer can be directly related to itsmolecular weight. Higher molecular weights are typically associatedwith, for example, higher Tg values and melt viscosities. The physicalproperties of a polymer having a broad molecular weight distribution,e.g., having a polydispersity index (PDI) in excess of 2.0 or 2.5, canbe characterized as an average of the individual physical properties ofand indeterminate interactions between the various polymeric speciesthat comprise it. As such, the physical properties of polymers havingbroad molecular weight distributions can be variable and hard tocontrol.

[0007] The polymer chain structure, or architecture, of a copolymer canbe described as the sequence of monomer residues along the polymer backbone or chain. For example, an epoxy functional copolymer prepared bystandard radical polymerization techniques will contain a mixture ofpolymer molecules having varying individual epoxy equivalent weights.Some of these polymer molecules can actually be free of epoxyfunctionality. In a thermosetting composition, the formation of a threedimensional crosslinked network is dependent upon the functionalequivalent weight as well as the architecture of the individual polymermolecules that comprise it. Polymer molecules having little or noreactive functionality (or having functional groups that are unlikely toparticipate in crosslinking reactions due to their location along thepolymer chain) will contribute little or nothing to the formation of thethree dimensional crosslink network, resulting in less than optimumphysical properties of the finally formed polymerizate, e.g., a cured orthermoset coating.

[0008] The continued development of new and improved epoxy based powdercoatings compositions having essentially zero VOC levels and acombination of favorable performance properties is desirable. Inparticular, it would be desirable to develop epoxy based powder coatingscompositions that comprise epoxy functional polymers having well definedmolecular weights and polymer chain structure, and narrow molecularweight distributions, e.g., PDI values less than 2.5. Controlling theepoxy polymer architecture and polydispersity is desirable in that itenables one to achieve higher Tg's and lower melt viscosities thancomparable epoxy polymers prepared by conventional processes, resultingin thermosetting particulate compositions which are resistant to cakingand have improved physical properties.

[0009] International patent publication WO 97/18247 and U.S. Pat. Nos.5,763,548 and 5,789,487 describe a radical polymerization processreferred to as atom transfer radical polymerization (ATRP). The ATRPprocess is described as being a living radical polymerization thatresults in the formation of (co)polymers having predictable molecularweight and molecular weight distribution. The ATRP process is alsodescribed as providing highly uniform products having controlledstructure (i.e., controllable topology, composition, etc.). The '548 and'487 patents and WO 97/18247 patent publication also describe(co)polymers prepared by ATRP, which are useful in a wide variety ofapplications, for example, with paints and coatings.

SUMMARY OF THE INVENTION

[0010] In accordance with the present invention there is provided, athermosetting composition comprising a co-reactable solid, particulatemixture of:

[0011] (a) epoxy functional polymer prepared by atom transfer radicalpolymerization initiated in the presence of an initiator having at leastone radically transferable group, and in which said epoxy functionalpolymer contains at least one of the following polymer chain structuresI and II:

-[(M)_(p)-(G)_(q)]_(x)-  I

and

-[(G)_(q)-(M)_(p)]_(x)  II

[0012] wherein M is a residue, that is free of oxirane functionality, ofat least one ethylenically unsaturated radically polymerizable monomer;G is a residue, that has oxirane functionality, of at least oneethylenically unsaturated radically polymerizable monomer; p and qrepresent average numbers of residues occurring in a block of residuesin each polymer chain structure; and p, q and x are each individuallyselected for each structure such that said epoxy functional polymer hasa number average molecular weight of at least 250; and

[0013] (b) co-reactant having functional groups reactive with the epoxygroups of (a).

[0014] In accordance with the present invention, there is also provideda method of coating a substrate with the above described thermosettingcomposition.

[0015] There is further provided, in accordance with the presentinvention, a multi-component composite coating composition comprising abase coat deposited from a pigmented film-forming composition, and atransparent top coat applied over the base coat. The transparent topcoat comprises the above described thermosetting composition.

[0016] Other than in the operating examples, or where otherwiseindicated, all numbers expressing quantities of ingredients, reactionconditions, and so forth used in the specification and claims are to beunderstood as modified in all instances by the term “about.”

[0017] As used herein, the term “polymer” is meant to refer to bothhomopolymers, i.e., polymers made from a single monomer species, andcopolymers, i.e., polymers made from two or more monomer species.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Thermosetting compositions in accordance with the presentinvention, comprise one or more epoxy functional polymers. As usedherein and in the claims, by “epoxy functional polymer” is meant apolymer having two or more epoxy groups in terminal and/or pendentpositions that are capable of reacting and forming covalent bonds withcompounds containing functional groups reactive with epoxides, e.g.,hydroxyl, thiol, amine and carboxylic acid groups.

[0019] The epoxy functional polymer of the present invention is preparedby atom transfer radical polymerization (ATRP). The ATRP method isdescribed as a “living polymerization,” i.e., a chain-growthpolymerization that propagates with essentially no chain transfer andessentially no chain termination. The molecular weight of a polymerprepared by ATRP can be controlled by the stoichiometry of thereactants, i.e., the initial concentration of monomer(s) andinitiator(s). In addition, ATRP also provides polymers havingcharacteristics including, for example, narrow molecular weightdistributions, e.g., PDI values less than 2.5, and well defined polymerchain structure, e.g., block copolymers and alternating copolymers.

[0020] The ATRP process can be described generally as comprising:polymerizing one or more radically polymerizable monomers in thepresence of an initiation system; forming a polymer; and isolating theformed polymer. The initiation system comprises: an initiator having aradically transferable atom or group; a transition metal compound, i.e.,a catalyst, which participates in a reversible redox cycle with theinitiator; and a ligand, which coordinates with the transition metalcompound. The ATRP process is described in further detail ininternational patent publication WO 97/18247 and U.S. Pat. Nos.5,763,548 and 5,789,487.

[0021] In preparing epoxy functional polymers of the present invention,the initiator may be selected from the group consisting of linear orbranched aliphatic compounds, cycloaliphatic compounds, aromaticcompounds, polycyclic aromatic compounds, heterocyclic compounds,sulfonyl compounds, sulfenyl compounds, esters of carboxylic acids,polymeric compounds and mixtures thereof, each having at least oneradically transferable group, which is typically a halo group. Theinitiator may also be substituted with functional groups, e.g., oxyranylgroups, such as glycidyl groups. Additional useful initiators and thevarious radically transferable groups that may be associated with themare described on pages 42 through 45 of international patent publicationWO 97/18247.

[0022] Polymeric compounds (including oligomeric compounds) havingradically transferable groups may be used as initiators, and are hereinreferred to as “macroinitiators.” Examples of macroinitiators include,but are not limited to, polystyrene prepared by cationic polymerizationand having a terminal halide, e.g., chloride, and a polymer of2-(2-bromopropionoxy) ethyl acrylate and one or more alkyl(meth)acrylates, e.g., butyl acrylate, prepared by conventionalnon-living radical polymerization. Macroinitiators can be used in theATRP process to prepare graft polymers, such as grafted block copolymersand comb copolymers. A further discussion of macroinitiators is found onpages 31 through 38 of international patent publication WO 98/01480.

[0023] Preferably, the initiator may be selected from the groupconsisting of halomethane, methylenedihalide, haloform, carbontetrahalide, 1-halo-2,3-epoxypropane, methanesulfonyl halide,p-toluenesulfonyl halide, methanesulfenyl halide, p-toluenesulfenylhalide, 1-phenylethyl halide, C₁-C₆-alkyl ester of2-halo-C₁-C₆-carboxylic acid, p-halomethylstyrene,mono-hexakis(α-halo-C₁-C₆-alkyl)benzene, diethyl-2-halo-2-methylmalonate, ethyl 2-bromoisobutyrate and mixtures thereof. A particularlypreferred initiator is diethyl-2-bromo-2-methyl malonate.

[0024] Catalysts that may be used in preparing epoxy functional polymersof the present invention, include any transition metal compound that canparticipate in a redox cycle with the initiator and the growing polymerchain. It is preferred that the transition metal compound not formdirect carbon-metal bonds with the polymer chain. Transition metalcatalysts useful in the present invention may be represented by thefollowing general formula III,

TM^(n+)X_(n)  III

[0025] wherein TM is the transition metal, n is the formal charge on thetransition metal having a value of from 0 to 7, and X is a counterion orcovalently bonded component. Examples of the transition metal (TM)include, but are not limited to, Cu, Fe, Au, Ag, Hg, Pd, Pt, Co, Mn, Ru,Mo, Nb and Zn. Examples of X include, but are not limited to, halogen,hydroxy, oxygen, C₁-C₆-alkoxy, cyano, cyanato, thiocyanato and azido. Apreferred transition metal is Cu(I) and X is preferably halogen, e.g.,chloride. Accordingly, a preferred class of transition metal catalystsare the copper halides, e.g., Cu(I)Cl. It is also preferred that thetransition metal catalyst contain a small amount, e.g., 1 mole percent,of a redox conjugate, for example, Cu(II)Cl₂ when Cu(I)Cl is used.Additional catalysts useful in preparing the epoxy functional polymersof the present invention are described on pages 45 and 46 ofinternational patent publication WO 97/18247. Redox conjugates aredescribed on pages 27 through 33 of international patent publication WO97/18247.

[0026] Ligands that may be used in preparing epoxy functional polymersof the present invention, include, but are not limited to compoundshaving one or more nitrogen, oxygen, phosphorus and/or sulfur atoms,which can coordinate to the transition metal catalyst compound, e.g.,through sigma and/or pi bonds. Classes of useful ligands, include butare not limited to: unsubstituted and substituted pyridines andbipyridines; porphyrins; cryptands; crown ethers; e.g., 18-crown-6;polyamines, e.g., ethylenediamine; glycols, e.g., alkylene glycols, suchas ethylene glycol; carbon monoxide; and coordinating monomers, e.g.,styrene, acrylonitrile and hydroxyalkyl (meth)acrylates. A preferredclass of ligands are the substituted bipyridines, e.g.,4,4′-dialkyl-bipyridyls. Additional ligands that may be used inpreparing epoxy functional polymers of the present invention aredescribed on pages 46 through 53 of international patent publication WO97/18247.

[0027] In preparing the epoxy functional polymers of the presentinvention the amounts and relative proportions of initiator, transitionmetal compound and ligand are those for which ATRP is most effectivelyperformed. The amount of initiator used can vary widely and is typicallypresent in the reaction medium in a concentration of from 10⁻⁴moles/liter (M) to 3 M, for example, from 10⁻³ M to 10⁻¹ M. As themolecular weight of the epoxy functional polymer can be directly relatedto the relative concentrations of initiator and monomer(s), the molarratio of initiator to monomer is an important factor in polymerpreparation. The molar ratio of initiator to monomer is typically withinthe range of 10⁻⁴: 1 to 0.5:1, for example, 10⁻³:1 to 5×10⁻²:1.

[0028] In preparing the epoxy functional polymers of the presentinvention, the molar ratio of transition metal compound to initiator istypically in the range of 10⁻⁴:1 to 10:1, for example, 0.1:1 to 5:1. Themolar ratio of ligand to transition metal compound is typically withinthe range of 0.1:1 to 100:1, for example, 0.2:1 to 10:1.

[0029] Epoxy functional polymers useful in the thermosettingcompositions of the present invention may be prepared in the absence ofsolvent, i.e., by means of a bulk polymerization process. Generally, theepoxy functional polymer is prepared in the presence of a solvent,typically water and/or an organic solvent. Classes of useful organicsolvents include, but are not limited to, esters of carboxylic acids,ethers, cyclic ethers, C₅-C₁₀ alkanes, C₅-C₈ cycloalkanes, aromatichydrocarbon solvents, halogenated hydrocarbon solvents, amides,nitriles, sulfoxides, sulfones and mixtures thereof. Supercriticalsolvents, such as CO₂, C₁-C₄ alkanes and fluorocarbons, may also beemployed. A preferred class of solvents are the aromatic hydrocarbonsolvents, particularly preferred examples of which are xylene, and mixedaromatic solvents such as those commercially available from ExxonChemical America under the trademark SOLVESSO. Additional solvents aredescribed in further detail on pages 53 through 56 of internationalpatent publication WO 97/18247.

[0030] The epoxy functional polymer is typically prepared at a reactiontemperature within the range of 25° C. to 140° C., e.g., from 50° C. to100° C., and a pressure within the range of 1 to 100 atmospheres,usually at ambient pressure. The atom transfer radical polymerization istypically completed in less than 24 hours, e.g., between 1 and 8 hours.

[0031] When the epoxy functional polymer is prepared in the presence ofa solvent, the solvent is removed after the polymer has been formed, byappropriate means as are known to those of ordinary skill in the art,e.g., vacuum distillation. Alternatively, the polymer may beprecipitated out of the solvent, filtered, washed and dried according toknown methods. After removal of, or separation from, the solvent, theepoxy functional polymer typically has a solids (as measured by placinga 1 gram sample in a 110° C. oven for 60 minutes) of at least 95percent, and preferably at least 98 percent, by weight based on totalpolymer weight.

[0032] Prior to use in the thermosetting compositions of the presentinvention, the ATRP transition metal catalyst and its associated ligandare typically separated or removed from the epoxy functional polymer.Removal of the ATRP catalyst is achieved using known methods, including,for example, adding a catalyst binding agent to the a mixture of thepolymer, solvent and catalyst, followed by filtering. Examples ofsuitable catalyst binding agents include, for example, alumina, silica,clay or a combination thereof. A mixture of the polymer, solvent andATRP catalyst may be passed through a bed of catalyst binding agent.Alternatively, the ATRP catalyst may be oxidized in situ and retained inthe epoxy functional polymer.

[0033] The epoxy functional polymer may be selected from the groupconsisting of linear polymers, branched polymers, hyperbranchedpolymers, star polymers, graft polymers and mixtures thereof. The form,or gross architecture, of the polymer can be controlled by the choice ofinitiator and monomers used in its preparation. Linear epoxy functionalpolymers may be prepared by using initiators having one or two radicallytransferable groups, e.g., diethyl-2-halo-2-methyl malonate andα,α-dichloroxylene. Branched epoxy functional polymers may be preparedby using branching monomers, i.e., monomers containing radicallytransferable groups or more than one ethylenically unsaturated radicallypolymerizable group, e.g., 2-(2-bromopropionoxy)ethyl acrylate,p-chloromethylstyrene and diethyleneglycol bis(methacrylate).Hyperbranched epoxy functional polymers may be prepared by increasingthe amount of branching monomer used.

[0034] Star epoxy functional polymers may be prepared using initiatorshaving three or more radically transferable groups, e.g.,hexakis(bromomethyl)benzene. As is known to those of ordinary skill inthe art, star polymers may be prepared by core-arm or arm-core methods.In the core-arm method, the star polymer is prepared by polymerizingmonomers in the presence of the polyfunctional initiator, e.g.,hexakis(bromomethyl)benzene. Polymer chains, or arms, of similarcomposition and architecture grow out from the initiator core, in thecore-arm method.

[0035] In the arm-core method, the arms are prepared separately from thecore and optionally may have different compositions, architecture,molecular weight and PDI's. The arms may have different epoxy equivalentweights, and some may be prepared without any epoxy functionality. Afterthe preparation of the arms, they are attached to the core. For example,the arms may be prepared by ATRP using glycidyl functional initiators.These arms can then be attached to a core having three or more activehydrogen groups that are reactive with epoxides, e.g., carboxylic acidor hydroxyl groups. The core can be a molecule, such as citric acid, ora core-arm star polymer prepared by ATRP and having terminal reactivehydrogen containing groups, e.g., carboxylic acid, thiol or hydroxylgroups. The reactive hydrogen groups of the core may react with theresidue of the glycidyl functional initiator or with epoxy functionalityalong the backbone of the arms.

[0036] An example of a core prepared by ATRP methods that can be used asa core in an ATRP arm-core star polymer is described as follows. In thefirst stage, 6 moles of methyl methacrylate are polymerized in thepresence of one mole of 1,3,5-tris(bromomethyl)benzene. In the secondstage, 3 moles of 2-hydroxyethyl methacrylate are fed to the reactionmixture. Three living ATRP prepared arms of varying or equivalentcomposition, and each containing a single epoxide group, e.g., theresidue of an epoxide functional initiator, may be connected to thehydroxy terminated core by reaction between the hydroxy groups of thecore and the epoxide group in each of the arms. Residues having oxiranefunctionality can be introduced into the living arms of the arm-corestar polymer by continuing the ATRP process in the presence of oxiranefunctional ethylenically unsaturated radically polymerizable monomers,e.g., glycidyl methacrylate.

[0037] Epoxy functional polymers in the form of graft polymers may beprepared using a macroinitiator, as previously described herein. Graft,branched, hyperbranched and star polymers are described in furtherdetail on pages 79 through 91 of international patent publication WO97/18247.

[0038] The polydispersity index (PDI) of epoxy functional polymersuseful in the present invention, is typically less than 2.5, moretypically less than 2.0, and preferably less than 1.8, for example, 1.5.As used herein, and in the claims, “polydispersity index” is determinedfrom the following equation: (weight average molecular weight(Mw)/number average molecular weight (Mn)). A monodisperse polymer has aPDI of 1.0. Further, as used herein, Mn and Mw are determined from gelpermeation chromatography using polystyrene standards.

[0039] General polymer chain structures I and II together or separatelyrepresent one or more structures that comprise the polymer chain, orback bone, architecture of the epoxy functional polymer. Subscripts pand q of general polymer chain structures I and II represent averagenumbers of residues occurring in the M and G blocks of residuesrespectively. Subscript x represents the number of segments of M and Gblocks, i.e., x-segments. Subscripts p and q may each be the same ordifferent for each x-segment. The following are presented for thepurpose of illustrating the various polymer architectures that arerepresented by general polymer chain structures I and II.

[0040] Homoblock Polymer Architecture:

[0041] When x is 1, p is 0 and q is 5, general polymer chain structure Irepresents a homoblock of 5 G residues, as more specifically depicted bythe following general formula IV.

-(G)-(G)-(G)-(G)-(G)-  IV

[0042] Diblock Copolymer Architecture:

[0043] When x is 1, p is 5 and q is 5, general polymer chain structure Irepresents a diblock of 5 M residues and 5 G residues as morespecifically depicted by the following general formula V.

-(M)-(M)-(M)-(M)-(M)-(G)-(G)-(G)-(G)-(G)-  V

[0044] Alternating Copolymer Architecture:

[0045] When x is greater than 1, for example, 5, and p and q are each 1for each x-segment, polymer chain structure I represents an alternatingblock of M and G residues, as more specifically depicted by thefollowing general formula VI.

-(M)-(G)-(M)-(G)-(M)-(G)-(M)-(G)-(M)-(G)-  VI

[0046] Gradient Copolymer Architecture:

[0047] When x is greater than 1, for example, 3, and p and q are eachindependently within the range of, for example, 1 to 3, for eachx-segment, polymer chain structure I represents a gradient block of Mand G residues, as more specifically depicted by the following generalformula VII.

-(M)-(M)-(M)-(G)-(M)-(M)-(G)-(G)-(M)-(G)-(G)-(G)-  VII

[0048] Gradient copolymers can be prepared from two or more monomers byATRP methods, and are generally described as having architecture thatchanges gradually and in a systematic and predictable manner along thepolymer backbone. Gradient copolymers can be prepared by ATRP methods by(a) varying the ratio of monomers fed to the reaction medium during thecourse of the polymerization, (b) using a monomer feed containingmonomers having different rates of polymerization, or (c) a combinationof (a) and (b). Gradient copolymers are described in further detail onpages 72 through 78 of international patent publication WO 97/18247.

[0049] With further reference to general polymer chain structures I andII, M represents one or more types of residues that are free of oxiranefunctionality, and p represents the average total number of M residuesoccurring per block of M residues (M-block) within an x-segment. The-(M)_(p)- portion of general structures I and II represents (1) ahomoblock of a single type of M residue, (2) an alternating block of twotypes of M residues, (3) a polyblock of two or more types of M residues,or (4) a gradient block of two or more types of M residues.

[0050] For purposes of illustration, when the M-block is prepared from,for example, 10 moles of methyl methacrylate, the -(M)_(p)- portion ofstructures I and II represents a homoblock of 10 residues of methylmethacrylate. In the case where the M-block is prepared from, forexample, 5 moles of methyl methacrylate and 5 moles of butylmethacrylate, the -(M)_(p)- portion of general structures I and IIrepresents, depending on the conditions of preparation, as is known toone of ordinary skill in the art: (a) a diblock of 5 residues of methylmethacrylate and 5 residues of butyl methacrylate having a total of 10residues (i.e., p=10); (b) a diblock of 5 residues of butyl methacrylateand 5 residues of methyl methacrylate having a total of 10 residues; (c)an alternating block of methyl methacrylate and butyl methacrylateresidues beginning with either a residue of methyl methacrylate or aresidue of butyl methacrylate, and having a total of 10 residues; or (d)a gradient block of methyl methacrylate and butyl methacrylate residuesbeginning with either residues of methyl methacrylate or residues ofbutyl methacrylate having a total of 10 residues.

[0051] Also, with reference to general polymer chain structures I andII, G represents one or more types of residues that have oxiranefunctionality, and q represents the average total number of G residuesoccurring per block of G residues (G-block). Accordingly, the -(G)_(q)-portions of polymer chain structures I and II may be described in amanner similar to that of the -(M)_(p)- portions provided above.

[0052] Residue M of general polymer chain structures I and II is derivedfrom at least one ethylenically unsaturated radically polymerizablemonomer. As used herein and in the claims, “ethylenically unsaturatedradically polymerizable monomer” and like terms are meant to includevinyl monomers, allylic monomers, olefins and other ethylenicallyunsaturated monomers that are radically polymerizable.

[0053] Classes of vinyl monomers from which X may be derived include,but are not limited to, (meth)acrylates, vinyl aromatic monomers, vinylhalides and vinyl esters of carboxylic acids. As used herein and in theclaims, by “(meth)acrylate” and like terms is meant both methacrylatesand acrylates. Preferably, residue M is derived from at least one ofalkyl (meth)acrylates having from 1 to 20 carbon atoms in the alkylgroup. Specific examples of alkyl (meth)acrylates having from 1 to 20carbon atoms in the alkyl group from which residue M may be derivedinclude, but are not limited to, methyl (meth)acrylate, ethyl(meth)acrylate, 2-hydroxyethyl (meth)acrylate, propyl (meth)acrylate,2-hydroxypropyl (meth)acrylate, isopropyl (meth)acrylate, butyl(meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate,2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, isobornyl(meth)acrylate, cyclohexyl (meth)acrylate and 3,3,5-trimethylcyclohexyl(meth)acrylate.

[0054] Residue M may also be selected from monomers having more than one(meth)acrylate group, for example, (meth)acrylic anhydride anddiethyleneglycol bis((meth)acrylate). Residue M may also be selectedfrom alkyl (meth)acrylates containing radically transferable groups,which can act as branching monomers, for example,2-(2-bromopropionoxy)ethyl acrylate.

[0055] Specific examples of vinyl aromatic monomers from which M may bederived include, but are not limited to, styrene, p-chloromethylstyrene,divinyl benzene, vinyl naphthalene and divinyl naphthalene. Vinylhalides from which M may be derived include, but are not limited to,vinyl chloride and vinylidene fluoride. Vinyl esters of carboxylic acidsfrom which M may be derived include, but are not limited to, vinylacetate, vinyl butyrate, vinyl 3,4-dimethoxybenzoate and vinyl benzoate.

[0056] As used herein and in the claims, by “olefin” and like terms ismeant unsaturated aliphatic hydrocarbons having one or more doublebonds, such as obtained by cracking petroleum fractions. Specificexamples of olefins from which M may be derived include, but are notlimited to, propylene, 1-butene, 1,3-butadiene, isobutylene anddiisobutylene.

[0057] As used herein and in the claims, by “allylic monomer(s)” ismeant monomers containing substituted and/or unsubstituted allylicfunctionality, i.e., one or more radicals represented by the followinggeneral formula VIII,

H₂C═C(R₄)—CH₂—  VIII

[0058] wherein R₄ is hydrogen, halogen or a C₁ to C₄ alkyl group. Mostcommonly, R₄ is hydrogen or methyl and consequently general formula VIIIrepresents the unsubstituted (meth)allyl radical. Examples of allylicmonomers include, but are not limited to: (meth)allyl alcohol;(meth)allyl ethers, such as methyl (meth)allyl ether; allyl esters ofcarboxylic acids, such as (meth)allyl acetate, (meth)allyl butyrate,(meth)allyl 3,4-dimethoxybenzoate and (meth)allyl benzoate.

[0059] Other ethylenically unsaturated radically polymerizable monomersfrom which M may be derived include, but are not limited to: cyclicanhydrides, e.g., maleic anhydride, 1-cyclopentene-1,2-dicarboxylicanhydride and itaconic anhydride; esters of acids that are unsaturatedbut do not have α,β-ethylenic unsaturation, e.g., methyl ester ofundecylenic acid; and diesters of ethylenically unsaturated dibasicacids, e.g., diethyl maleate.

[0060] Residue G of general polymer chain structures I and II typicallyis derived from monomers having epoxy, i.e., epoxide or oxirane,functionality. Preferably residue G is derived from at least one ofglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate,2-(3,4-epoxycyclohexyl)ethyl (meth)acrylate and allyl glycidyl ether. Ina particularly preferred embodiment of the present invention, residue Gis derived from glycidyl methacrylate. Alternately, epoxy functionalitymay be incorporated into the epoxy functional polymer by post-reaction,such as by preparing a hydroxyl functional polymer and converting to anepoxy functional polymer by reacting with epichlorohydrin.

[0061] Subscripts p and q represent average number of residues occurringin a block of residues in each polymer structure. Typically, p and qeach independently have a value of 0 or more, preferably at least 1, andmore preferably at least 5 for each of general polymer structures I andII. Also, subscripts p and q each independently have a value oftypically less than 100, preferably less than 20, and more preferablyless than 15 for each of general polymer structures I and II. The valuesof subscripts p and q may range between any combination of these values,inclusive of the recited values. Moreover, the sum of p and q is atleast 1 within an x-segment and q is at least 1 within at least onex-segment in the polymer.

[0062] Subscript x of general polymer structures I and II typically hasa value of at least 1. Also, subscript x typically has a value of lessthan 100, preferably less than 50, and more preferably less than 10. Thevalue of subscript x may range between any combination of these values,inclusive of the recited values. If more than one of the structures Iand/or II occur in the polymer molecule, x may have different values foreach structure (as may p and q), allowing for a variety of polymerarchitectures such as gradient copolymers.

[0063] The epoxy functional polymer of the present invention may befurther described as having at least one of the following generalpolymer chain structures IX and X:

φ-[[(M)_(p)-(G)_(q)]_(x)-(M)_(r)-T]_(z)  IX

and

φ-[[(G)_(q)-(M)_(p)]_(x)-(G)_(s)-T]_(z)  X

[0064] wherein p, q, x, M and G have the same meanings as previouslydescribed herein. The subscripts r and s represent average numbers ofresidues occurring in the respective blocks of X and G residues. The-(M)_(r)- and -(G)_(s)- portions of general formulas IX and X havemeanings similar to those as previously described herein with regard toportions -(M)_(p)- and -(G)_(q)-.

[0065] The structures IX and X can represent the polymer itself or,alternatively, each of the structures can comprise a terminal segment ofthe polymer. For example, where z is 1, the structures IX and X canrepresent a linear polymer, prepared by ATRP using an initiator having 1radically transferable group. Where z is 2, the structures IX and X canrepresent a linear “leg” extending from the residue of an initiatorhaving 2 radically transferable groups. Alternatively, where z isgreater than 2, the structures IX and X can each represent an “arm” of astar polymer prepared by ATRP, using an initiator having more than 2radically transferable groups.

[0066] Symbol φ of general formulas IX and X is or is derived from theresidue of the initiator used in the ATRP preparation of the polymer,and is free of the radically transferable group of the initiator. Forexample, when the epoxy functional polymer is initiated in the presenceof benzyl bromide, the symbol φ, more specifically φ-, is the benzylresidue,

[0067] The symbol φ may also be derived from the residue of theinitiator. For example, when the epoxy functional polymer is initiatedusing epichlorohydrin the symbol φ, more

[0068] specifically φ-, is the 2,3-epoxy-propyl residue, The2,3-epoxy-propyl residue can then be converted to, for example, a2,3-dihydroxypropyl residue. Derivations or conversions of the initiatorresidue are preferably performed at a point in the ATRP process whenloss of epoxide functionality along the polymer backbone is minimal, forexample, prior to incorporating a block of residues having epoxyfunctionality.

[0069] In general formulas IX and X, subscript z is equal to the numberof epoxy functional polymer chains that are attached to φ. Subscript zis at least 1 and may have a wide range of values. In the case of combor graft polymers, wherein 4 is a macroinitiator having several pendentradically transferable groups, z can have a value in excess of 10, forexample 50, 100 or 1000. Typically, z is less than 10, preferably lessthan 6 and more preferably less than 5. In a preferred embodiment of thepresent invention, z is 1 or 2.

[0070] Symbol T of general formulas IX and X is or is derived from theradically transferable group of the initiator. For example, when theepoxy functional polymer is prepared in the presence ofdiethyl-2-bromo-2-methyl malonate, T may be the radically transferablebromo group.

[0071] The radically transferable group may optionally be (a) removed or(b) chemically converted to another moiety. In either of (a) or (b), thesymbol T is considered herein to be derived from the radicallytransferable group of the initiator. The radically transferable groupmay be removed by substitution with a nucleophilic compound, e.g., analkali metal alkoxylate. However, in the present invention, it isdesirable that the method by which the radically transferable group iseither removed or chemically converted also be relatively mild withregard to the epoxy functionality of the polymer. Many nucleophilicsubstitution reactions can result in loss of epoxy functionality fromthe polymer.

[0072] In a preferred embodiment of the present invention, when theradically transferable group is a halogen, the halogen can be removed bymeans of a mild dehalogenation reaction, which does not reduce the epoxyfunctionality of the polymer. The reaction is typically performed as apost-reaction after the polymer has been formed, and in the presence ofat least an ATRP catalyst. Preferably, the dehalogenation post-reactionis performed in the presence of both an ATRP catalyst and its associatedligand.

[0073] The mild dehalogenation reaction is performed by contacting thehalogen terminated epoxy functional polymer of the present inventionwith one or more ethylenically unsaturated compounds, which are notreadily radically polymerizable under at least a portion of the spectrumof conditions under which atom transfer radical polymerizations areperformed, hereinafter referred to as “limited radically polymerizableethylenically unsaturated compounds” (LRPEU compound). As used herein,by “halogen terminated” and similar terms is meant to be inclusive alsoof pendent halogens, e.g., as would be present in branched, comb andstar polymers.

[0074] Not intending to be bound by any theory, it is believed, based onthe evidence at hand, that the reaction between the halogen terminatedepoxy functional polymer and one or more LRPEU compounds results in (1)removal of the terminal halogen group, and (2) the addition of at leastone carbon-carbon double bond where the terminal carbon-halogen bond isbroken. The dehalogenation reaction is typically conducted at atemperature in the range of 0° C. to 200° C., e.g., from 0° C. to 160°C., a pressure in the range of 0.1 to 100 atmospheres, e.g., from 0.1 to50 atmospheres. The reaction is also typically performed in less than 24hours, e.g., between 1 and 8 hours. While the LRPEU compound may beadded in less than a stoichiometric amount, it is preferably added in atleast a stoichiometric amount relative to the moles of terminal halogenpresent in the epoxy functional polymer. When added in excess of astoichiometric amount, the LRPEU compound is typically present in anamount of no greater than 5 mole percent, e.g., 1 to 3 mole percent, inexcess of the total moles of terminal halogen.

[0075] Limited radically polymerizable ethylenically unsaturatedcompounds useful for dehalogenating the epoxy functional polymer of thecomposition of the present invention under mild conditions include thoserepresented by the following general formula XI.

[0076] In general formula XI, R₁ and R₂ can be the same or differentorganic groups such as: alkyl groups having from 1 to 4 carbon atoms;aryl groups; alkoxy groups; ester groups; alkyl sulfur groups; acyloxygroups; and nitrogen-containing alkyl groups where at least one of theR₁ and R₂ groups is an organo group while the other can be an organogroup or hydrogen. For instance when one of R₁ or R₂ is an alkyl group,the other can be an alkyl, aryl, acyloxy, alkoxy, arenes,sulfur-containing alkyl group, or nitrogen-containing alkyl and/ornitrogen-containing aryl groups. The R₃ groups can be the same ordifferent groups selected from hydrogen or lower alkyl selected suchthat the reaction between the terminal halogen of the epoxy functionalpolymer and the LRPEU compound is not prevented. Also an R₃ group can bejoined to the R₁ and/or the R₂ groups to form a cyclic compound.

[0077] It is preferred that the LRPEU compound be free of halogengroups. Examples of suitable LRPEU compounds include, but are notlimited to, 1,1-dimethylethylene, 1,1-diphenylethylene, isopropenylacetate, alpha-methyl styrene, 1,1-dialkoxy olefin and mixtures thereof.Additional examples include dimethyl itaconate and diisobutene(2,4,4-trimethyl-1-pentene).

[0078] For purposes of illustration, the reaction between halogenterminated epoxy functional polymer and LRPEU compound, e.g.,alpha-methyl styrene, is summarized in the following general scheme 1.

[0079] In general scheme 1, P-X represents the halogen terminated epoxyfunctional polymer.

[0080] For each of general polymer structures IX and X, the subscripts rand s each independently have a value of 0 or more. Subscripts r and seach independently have a value of typically less than 100, preferablyless than 50, and more preferably less than 10, for each of generalpolymer structures IX and X. The values of r and s may each rangebetween any combination of these values, inclusive of the recitedvalues.

[0081] The epoxy functional polymer typically has an epoxy equivalentweight of at least 128 grams/equivalent, and preferably at least 200grams/equivalent. The epoxy equivalent weight of the polymer is alsotypically less than 10,000 grams/equivalent, preferably less than 5,000grams/equivalent, and more preferably less than 1,000 grams/equivalent.The epoxy equivalent weight of the epoxy functional polymer may rangebetween any combination of these values, inclusive of the recitedvalues.

[0082] The number average molecular weight (Mn) of the epoxy functionalpolymer is typically at least 250, more typically at least 500,preferably at least 1000, and more preferably at least 2000. The epoxyfunctional polymer also typically has a Mn of less than 16,000,preferably less than 10,000, and more preferably less than 5,000. The Mnof the epoxy functional polymer may range between any combination ofthese values, inclusive of the recited values.

[0083] The epoxy functional polymer may be used in the thermosettingcomposition of the present invention as a resinous binder or as anadditive with a separate resinous binder, which may be prepared by ATRPor by conventional polymerization methods. When used as an additive, theepoxy functional polymer as described herein typically has lowfunctionality, e.g., it may be monofunctional, and a correspondinglyhigh equivalent weight.

[0084] The epoxy functional polymer is typically present in thethermosetting composition of the present invention in an amount of atleast 0.5 percent by weight, more typically at least 30 percent byweight, preferably at least 50 percent by weight, and more preferably atleast 60 percent by weight, based on total weight of resin solids of thethermosetting composition. The thermosetting composition also typicallycontains epoxy functional polymer present in an amount of less than 99.5percent by weight, more typically less than 95 by weight, preferablyless than 90 percent by weight, and more preferably less than 80 percentby weight, based on total weight of resin solids of the thermosettingcomposition. The epoxy functional polymer may be present in thethermosetting composition of the present invention in an amount rangingbetween any combination of these values, inclusive of the recitedvalues.

[0085] The thermosetting composition of the present invention alsocomprises one or more co-reactants having functional groups that arereactive with the epoxy functionality of the epoxy functional polymer.The co-reactant (b) of the composition is not prepared by atom transferradical polymerization methods. The co-reactant may have functionalgroups selected from the group consisting of hydoxyl, thiol, primaryamines, secondary amines, carboxyl and mixtures thereof. Usefulco-reactants having amine functionality include, for example,dicyandiamide and substituted dicyandiamides. Preferably, theco-reactant has carboxylic acid groups. In one embodiment of the presentinvention, the co-reactant has carboxylic acid functionality and issubstantially crystalline. By “crystalline” is meant that theco-reactant contains at least some crystalline domains, andcorrespondingly may contain some amorphous domains. While not necessary,it is preferred that the co-reactant have a melt viscosity less thanthat of the epoxy functional polymer (at the same temperature). As usedherein and in the claims, by “functional groups reactive with the epoxygroups of the epoxy functional polymer” is meant that the co-reactanthas at least two functional groups that are reactive with epoxyfunctionality.

[0086] Preferably, the co-reactant is a carboxylic acid functionalco-reactant, which typically contains from 4 to 20 carbon atoms.Examples of co-reactants useful in the present invention include, butare not limited to, dodecanedioic acid, azelaic acid, adipic acid,1,6-hexanedioic acid, succinic acid, pimelic acid, sebasic acid, maleicacid, citric acid, itaconic acid, aconitic acid and mixtures thereof.

[0087] Other suitable carboxylic acid functional co-reactants includethose represented by the following general formula XII,

[0088] In general formula XII, R is the residue of a polyol, E is adivalent linking group having from 1 to 10 carbon atoms, and n is aninteger of from 2 to 10. Examples of polyols from which R of generalformula XII may be derived include, but are not limited to, ethyleneglycol, di(ethylene glycol), trimethylolethane, trimethylolpropane,pentaerythritol, di-trimethylolpropane, di-pentaerythritol and mixturesthereof. Divalent linking groups from which E may be selected include,but are not limited to, methylene, ethylene, propylene, isopropylene,butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene,cyclohexylene, e.g., 1,2-cyclohexylene, substituted cyclohexylene, e.g.,4-methyl-1,2-cyclohexylene, phenylene, e.g., 1,2-phenylene, andsubstituted phenylene, e.g., 4-methyl-1,2-phenylene and 4-carboxylicacid-1,2-phenylene. The divalent linking group E is preferablyaliphatic.

[0089] The co-reactant represented by general formula XII is typicallyprepared from a polyol and a dibasic acid or cyclic anhydride. Forexample, trimethylol propane and hexahydro-4-methylphthalic anhydrideare reacted together in a molar ratio of 1:3 respectively, to form acarboxylic acid functional co-reactant. This particular co-reactant canbe described with reference to general formula XII as follows, R is theresidue of trimethylol propane, E is the divalent linking group4-methyl-1,2-cyclohexylene, and n is 3. Carboxylic acid functionalco-reactants described herein with reference to general formula XII aremeant to include also any unreacted starting materials and/orco-products, e.g., oligomeric species, resulting from their preparationand contained therein.

[0090] The co-reactant is typically present in the thermosettingcompositions of the present invention in an amount of at least 10percent by weight, and preferably at least 15 percent by weight, basedon total resin solids weight of the composition. The co-reactant is alsotypically present in the composition in an amount of less than 70percent by weight, more typically less than 50 percent by weight,preferably less than 30 percent by weight, and more preferably less than25 percent by weight, based on total resin solids weight of thecomposition. The amount of co-reactant present in the thermosettingcomposition of the present invention may range between any combinationof these values, inclusive of the recited values.

[0091] The equivalent ratio of epoxy equivalents in the epoxy functionalpolymer (a) to the equivalents of reactive functional groups in theco-reactant (b) is typically from 0.5:1 to 2:1, and preferably from0.8:1 to 1.5:1. While equivalent ratios outside of these ranges arewithin the scope of the present invention, they are generally lessdesirable due to appearance and performance deficiencies in cured filmsobtained therefrom.

[0092] The thermosetting composition of the present invention usuallyalso includes one or more cure catalysts for catalyzing the reactionbetween the reactive functional groups of the co-reactant and the epoxygroups of the polymer. Examples of cure catalysts for acid functionalco-reactants are the tertiary amines, e.g., methyl dicocoamine, and tincompounds, e.g., triphenyl tin hydroxide. Curing catalyst is typicallypresent in the thermosetting composition in an amount of less than 5percent by weight, e.g., from 0.25 percent by weight to 2.0 percent byweight, based on total resin solids weight of the composition.

[0093] Thermosetting compositions according to the present invention mayoptionally include one or more co-curatives that are different than theco-reactant (b), and are not prepared by ATRP methods. As used herein,by “co-curative” is meant a compound that has functionality that is notreactive with the epoxide groups of the epoxy functional polymer (a).For example, the co-curative may have functional groups that arereactive with: the functional groups of the co-reactant (b); and/or thehydroxyl groups formed as a result of reaction between the functionalgroups of the co-reactant (b) and the epoxide groups of the epoxyfunction polymer (a). Co-curatives may be included in the composition tooptimize physical properties (e.g., impact, scratch and crackresistance) of polymerizates obtained therefrom. If used, co-curativesare typically present in the composition in amounts of less than 10percent by weight, e.g., from 1 to 5 percent by weight, based on totalresin solids weight of the thermosetting composition. A useful class ofco-curatives are capped polyisocyanates having two or more cappedisocyanate groups, which are know to those of ordinary skill in the art.An example of a particularly useful capped polyisocyanate co-curative isa trimer of 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane(isophorone diisocyanate or IPDI) capped with 2-butanone oxime ore-caprolactam.

[0094] The thermosetting composition of the present invention may alsoinclude pigments and fillers. Examples of pigments include, but are notlimited to, inorganic pigments, e.g., titanium dioxide and iron oxides,organic pigments, e.g., phthalocyanines, anthraquinones, quinacridonesand thioindigos, and carbon blacks. Examples of fillers include, but arenot limited to, silica, e.g., precipitated silicas, clay, and bariumsulfate. When used in the composition of the present invention, pigmentsand fillers are typically present in amounts of from 0.1 percent to 70percent by weight, based on total weight of the thermosettingcomposition. More often, the thermosetting composition of the presentinvention is used as a clear composition being substantially free ofpigments and fillers.

[0095] The thermosetting composition of the present invention mayoptionally contain additives such as waxes for flow and wetting,degassing additives such as benzoin, adjuvant resin to modify andoptimize coating properties and ultraviolet (UV) light absorbers. Theseoptional additives, when used, are typically present in amounts up to 20percent by weight, based on total weight of resin solids of thethermosetting composition.

[0096] The thermosetting composition of the present invention istypically prepared by first dry blending the epoxy functional polymer,the co-reactant and additives, such as flow control agents, degassingagents and catalysts, in a blender, e.g., a Henshel blade blender. Theblender is operated for a period of time sufficient to result in ahomogenous dry blend of the materials charged thereto. The homogenousdry blend is then melt blended in an extruder, e.g., a twin screwco-rotating extruder, operated within a temperature range of 80° C. to140° C., e.g., from 100° C. to 125° C.

[0097] Optionally, the thermosetting composition may be melt blended intwo or more steps. For example, a first melt blend is prepared in theabsence of cure catalyst. A second melt blend is prepared at a lowertemperature, from a dry blend of the first melt blend and the curecatalyst. When used as a powder coating composition, the melt blendedthermosetting composition is typically milled to an average particlesize of from, for example, 15 to 30 microns.

[0098] In accordance with the present invention there is also provided,a method of coating a substrate comprising:

[0099] (a) applying to said substrate a thermosetting composition;

[0100] (b) coalescing said thermosetting composition to form asubstantially continuous film; and

[0101] (c) curing said thermosetting composition by the application ofheat, wherein said thermosetting composition comprises a co-reactablesolid, particulate mixture as previously described herein.

[0102] The thermosetting composition of the present invention may beapplied to the substrate by any appropriate means that are known tothose of ordinary skill in the art. Generally, the thermosettingcomposition is in the form of a dry powder and is applied by sprayapplication. Alternatively, the powder can be slurried in a liquidmedium such as water, and spray applied. Where the language“co-reactable solid, particulate mixture” is used in the specificationand claims, the thermosetting composition can be in dry powder form orin the form of a slurry.

[0103] When the substrate is electrically conductive, the thermosettingcomposition is typically electrostatically applied. Electrostatic sprayapplication generally involves drawing the thermosetting compositionfrom a fluidized bed and propelling it through a corona field. Theparticles of the thermosetting composition become charged as they passthrough the corona field and are attracted to and deposited upon theelectrically conductive substrate, which is grounded. As the chargedparticles begin to build up, the substrate becomes insulated, thuslimiting further particle deposition. This insulating phenomenontypically limits the film build of the deposited composition to amaximum of 3 to 6 mils (75 to 150 microns).

[0104] Alternatively, when the substrate is not electrically conductive,for example as is the case with many plastic substrates, the substrateis typically preheated prior to application of the thermosettingcomposition. The preheated temperature of the substrate is equal to orgreater than that of the melting point of the thermosetting composition,but less than its cure temperature. With spray application overpreheated substrates, film builds of the thermosetting composition inexcess of 6 mils (150 microns) can be achieved, e.g., 10 to 20 mils (254to 508 microns). Substrates that may be coated by the method of thepresent invention include, for example, ferrous substrates, aluminumsubstrates, plastic substrates, e.g., sheet molding compound basedplastics, and wood.

[0105] After application to the substrate, the thermosetting compositionis then coalesced to form a substantially continuous film. Coalescing ofthe applied composition is generally achieved through the application ofheat at a temperature equal to or greater than that of the melting pointof the composition, but less than its cure temperature. In the case ofpreheated substrates, the application and coalescing steps can beachieved in essentially one step.

[0106] The coalesced thermosetting composition is next cured by theapplication of heat. As used herein and in the claims, by “cured” ismeant a three dimensional crosslink network formed by covalent bondformation, e.g., between the reactive functional groups of theco-reactant and the epoxy groups of the polymer. The temperature atwhich the thermosetting composition of the present invention cures isvariable and depends in part on the type and amount of catalyst used.Typically, the thermosetting composition has a cure temperature withinthe range of 130° C. to 160° C., e.g., from 140° C. to 150° C.

[0107] In accordance with the present invention there is furtherprovided, a multi-component composite coating composition comprising:

[0108] (a) a base coat deposited from a pigmented film-formingcomposition; and

[0109] (b) a transparent top coat applied over said base coat, whereinsaid transparent top coat is deposited from a clear film-formingthermosetting composition comprising a co-reactable solid, particulatemixture as previously described herein. The multi-component compositecoating composition as described herein is commonly referred to as acolor-plus-clear coating composition.

[0110] The pigmented film-forming composition from which the base coatis deposited can be any of the compositions useful in coatingsapplications, particularly automotive applications in whichcolor-plus-clear coating compositions are extensively used. Pigmentedfilm-forming compositions conventionally comprise a resinous binder anda pigment to act as a colorant. Particularly useful resinous binders areacrylic polymers, polyesters including alkyds, and polyurethanes.

[0111] The resinous binders for the pigmented film-forming base coatcomposition can be organic solvent-based materials such as thosedescribed in U.S. Pat. No. 4,220,679, note column 2 line 24 throughcolumn 4, line 40. Also, water-based coating compositions such as thosedescribed in U.S. Pat. Nos. 4,403,003, 4,147,679 and 5,071,904 can beused as the binder in the pigmented film-forming composition.

[0112] The pigmented film-forming base coat composition is colored andmay also contain metallic pigments. Examples of suitable pigments can befound in U.S. Pat. Nos. 4,220,679, 4,403,003, 4,147,679 and 5,071,904.

[0113] Ingredients that may be optionally present in the pigmentedfilm-forming base coat composition are those which are well known in theart of formulating surface coatings and include surfactants, flowcontrol agents, thixotropic agents, fillers, anti-gassing agents,organic co-solvents, catalysts, and other customary auxiliaries.Examples of these optional materials and suitable amounts are describedin the aforementioned U.S. Pat. Nos. 4,220,679, 4,403,003, 4,147,769 and5,071,904.

[0114] The pigmented film-forming base coat composition can be appliedto the substrate by any of the conventional coating techniques such asbrushing, spraying, dipping or flowing, but are most often applied byspraying. The usual spray techniques and equipment for air spraying,airless spray and electrostatic spraying employing either manual orautomatic methods can be used. The pigmented film-forming composition isapplied in an amount sufficient to provide a base coat having a filmthickness typically of 0.1 to 5 mils (2.5 to 125 microns) and preferably0.1 to 2 mils (2.5 to 50 microns).

[0115] After deposition of the pigmented film-forming base coatcomposition on to the substrate, and prior to application of thetransparent top coat, the base coat can be cured or alternatively dried.In drying the deposited base coat, organic solvent and/or water, isdriven out of the base coat film by heating or the passage of air overits surface. Suitable drying conditions will depend on the particularbase coat composition used and on the ambient humidity in the case ofcertain water-based compositions. In general, drying of the depositedbase coat is performed over a period of from 1 to 15 minutes and at atemperature of 21° C. to 93° C.

[0116] The transparent top coat is applied over the deposited base coatby any of the methods by which powder coatings are known to be applied.Preferably the transparent top coat is applied by electrostatic sprayapplication, as described previously herein. When the transparent topcoat is applied over a deposited base coat that has been dried, the twocoatings can be co-cured to form the multi-component composite coatingcomposition of the present invention. Both the base coat and top coatare heated together to conjointly cure the two layers. Typically, curingconditions of 130° C. to 160° C. for a period of 20 to 30 minutes areemployed. The transparent top coat typically has a thickness within therange of 0.5 to 6 mils (13 to 150 microns), e.g., from 1 to 3 mils (25to 75 microns).

[0117] The present invention is more particularly described in thefollowing examples, which are intended to be illustrative only, sincenumerous modifications and variations therein will be apparent to thoseskilled in the art. Unless otherwise specified, all parts andpercentages are by weight.

SYNTHESIS EXAMPLES A-D

[0118] Synthesis Examples A-D describe the preparation of epoxyfunctional acrylic polymers that are used in the powder coatingcompositions of Examples 1-4. The epoxy functional polymer of Example Ais a comparative polymer prepared by non-living radical polymerization.The epoxy functional polymers of Examples B-D are representative ofpolymers useful in the thermosetting coating compositions of the presentinvention. The physical properties of the polymers of Examples A-D aresummarized in Table 1.

[0119] In synthesis Examples A-D, the following monomer abbreviationsare used: glycidyl methacrylate (GMA); iso-butyl methacrylate (IBMA);and iso-bornyl methacrylate (IBoMA). The molar ratio of GMA to IBMA toIBoMA was 6:4:2 in each of Synthesis Examples A-D. The block copolymerstructures shown in each of Examples B-D are representative generalblock copolymer formulas.

EXAMPLE A

[0120] A comparative epoxy functional polymer was prepared by standard,i.e., non-controlled or non-living, radical polymerization from theingredients enumerated in Table A. TABLE A Ingredients Parts by weightCharge 1 xylene 1199.3 Charge 2 GMA 2183.3 IBoMA 1164.4 IBMA 1504.0Charge 3 xylene 443.1 initiator (a) 485.2 Charge 4 xylene 186.7 Charge 5xylene 23.1 initiator (a) 23.1

[0121] Charge 1 was heated to reflux temperature at atmospheric pressureunder a nitrogen blanket in a 12 liter round bottom flask equipped witha rotary blade agitator, reflux condenser, thermometer and heatingmantle coupled together in a feed-back loop through a temperaturecontroller, nitrogen inlet port, and two addition ports. While underconditions of reflux, Charges 2 and 3 were concurrently fed into theflask over a period of 3 hours and 3.5 hours respectively. With theaddition of Charges 2 and 3 complete, Charge 4 was divided into twoequal parts and used to rinse any residual material remaining in theaddition funnels of Charges 2 and 3 into the flask. Charge 5 was thenfed into the flask, followed by a two hour hold under reflux conditions.The contents of the flask were then vacuum stripped. While still molten,the stripped contents of the flask were transferred to a suitableshallow open container and allowed to cool to room temperature andharden.

EXAMPLE B

[0122] An epoxy functional pentablock copolymer useful in thethermosetting compositions of the present invention was prepared by atomtransfer radical polymerization from the ingredients listed in Table B.The epoxy functional block copolymer of this example is summarizeddiagrammatically as follows:

(IBMA)₂-(GMA)₃-(IBMA)₂-(GMA)₃-(IBoMA)₂ TABLE B Ingredients Parts byweight Charge 1 toluene 158.8 copper (II) bromide (b) 10.9 copper powder(c) 44.5 2,2′-bypyridyl 15.31 diethyl-2-bromo-2-methylmalonate 177 .2IBMA 198.8 Charge 2 toluene 158.8 GMA 298.2 Charge 3 toluene 158.8 IMBA198.8 Charge 4 toluene 158.9 GMA 290.2 Charge 5 toluene 158.9 IBoMA311.2

[0123] Charge 1 was heated to and held at 90° C. for one hour in a 2liter 4-necked flask equipped with a motor driven stainless steel stirblade, water cooled condenser, and a heating mantle and thermometerconnected through a temperature feed-back control device. The contentsof the flask were cooled to 70° C. and charge 2 was added over a periodof 15 minutes, followed by a 1 hour hold at 70° C. The contents of theflask were next heated to 90° C. and Charge 3 was added over a period of15 minutes, followed by a 1 hour hold at 90° C. Charge 4 was then addedover a period of 15 minutes after cooling the contents of the flask to70° C., followed by a 1 hour hold at 70° C. After heating the contentsof the flask to 90° C., Charge 5 was added over a period of 15 minutes,followed by a 2 hour hold at 90° C. Upon cooling to room temperature,the contents of the flask were filtered and then vacuum stripped. Whilestill molten, the stripped contents of the flask were transferred to asuitable shallow open container and allowed to cool to room temperatureand harden.

EXAMPLE C

[0124] An epoxy functional tetrablock copolymer useful in thethermosetting compositions of the present invention was prepared by atomtransfer radical polymerization from the ingredients listed in Table C.The epoxy functional block copolymer of this example is summarizeddiagrammatically as follows:

(GMA)₃-(IBMA)₄-(GMA)₃-(IBoMA)₂ TABLE C Ingredients Parts by weightCharge 1 toluene 158 .8 copper (II) bromide (b) 10.9 copper powder (c)44.5 2,2′-bypyridyl 15.31 diethyl-2-bromo-2-methylmalonate 177.2 GMA298.2 Charge 2 toluene 158.9 IBMA 398.2 Charge 3 toluene 158.9 GMA 298.2Charge 4 toluene 158.9 IBoMA 311.2

[0125] Charge 1 was heated to and held at 70° C. for one hour in a 2liter 4-necked flask equipped as described in Example B. The contents ofthe flask were heated to 90° C., and Charge 2 was added over a period of15 minutes, followed by a 1.5 hour hold at 90° C. After cooling thecontents of the flask to 70° C., Charge 3 was added over a period of 15minutes, followed by a 1 hour hold at 70° C. Upon heating the contentsof the flask to 90° C., Charge 4 was added over a period of 15 minutes,followed by a 2 hour hold at 90° C. The contents of the flask werecooled, filtered and vacuum stripped as described in Example B.

EXAMPLE D

[0126] An epoxy functional hexablock copolymer useful in thethermosetting compositions of the present invention was prepared by atomtransfer radical polymerization from the ingredients enumerated in TableD. The epoxy functional block copolymer of this example is summarizeddiagrammatically as follows:

(GMA)₂-(IBMA)₂-(GMA)₂-(IBMA)₂-(GMA)₂-(IBoMA)₂ TABLE D Ingredients Partsby weight Charge 1 toluene 127.0 copper (II) bromide (b) 10.9 copperpowder (c) 44.5 2,2′-bypyridyl 15.31 diethyl-2-bromo-2-methylmalonate177.2 GMA 198.8 Charge 2 toluene 127.0 IBMA 199.1 Charge 3 toluene 127.0GMA 198.8 Charge 4 toluene 127.0 IMBA 199.1 Charge 5 toluene 127.0 GMA198.8 Charge 6 toluene 127.0 IBoMA 311.2

[0127] Charge 1 was heated to and held at 70° C. for one hour in a 2liter 4-necked flask equipped as described in Example B. The contents ofthe flask were heated to 90° C. and Charge 2 was added over a period of15 minutes, followed by a 1 hour hold at 90° C. Upon cooling thecontents of the flask to 70° C., Charge 3 was added over 15 minutes andthen held at 70° C. for 1 hour. After heating the contents of the flaskto 90° C., Charge 4 was added over 15 minutes and then held at 90° C.for 1 hour. The contents of the flask were cooled to 70° C. and Charge 5was added over 15 minutes followed by a 1 hour hold at 70° C. Uponheating the contents of the flask to 90° C., Charge 6 was added over 15minutes followed by a hold at 90° C. for 2 hours. The contents of theflask were cooled, filtered and vacuum stripped as described in ExampleB. TABLE 1 Physical Data of the Polymers of Synthesis Examples A-DExample Example A Example B C Example D Mn (d) 1369 2448 2087 2300 Mw2873 3538 2803 3482 Mz 4588 4689 3477 4642 Mp 2927 3499 2986 3622 PDI(e) 2.1 1.4 1.3 1.5 Tg midpoint (° C.) 25.3 41.3 43.9 34.2 (f) MeltViscosity 129 655 689 467 at 125° C. (poise) (g) Melt Viscosity 90 439461 323 at 130° C. (Poise) Melt Viscosity 64 286 296 213 at 135° C.(poise) Melt Viscosity 48 190 194 146 at 140° C. (poise) Melt Viscosity36 131 133 103 at 145° C. (poise) Melt Viscosity 28 87 87 71 at 150° C.(poise) Epoxy Equivalent 327 370 380 390 Weight (h) Percent Weight 99.699.6 99.5 99.6 Solids (i)

POWDER COATING EXAMPLES 1-4

[0128] Powder coating Examples 2-4 are representative of thermosettingcoating compositions according to the present invention, while powdercoating Example 1 is a comparative example. The powder coatingcompositions were prepared from the ingredients enumerated in Table 2.TABLE 2 Powder Coating Compositions Ingredient Example 1 Example 2Example 3 Example 4 Polymer of 682.0 0 0 0 Example A Polymer of 0 715.20 0 Example B Polymer of 0 0 715.2 0 Example C Polymer of 0 0 0 715.2Example D DDDA (j) 236.3 203.1 203.1 203.1 Flow Control 10.0 10.0 10.010.0 Agent (k) Benzoin 2.0 2.0 2.0 2.0 Wax (l) 6.0 6.0 6.0 6.0 UVStabilizer-1 20.0 20.0 20.0 20.0 (m) UV Stabilizer-2 20.0 20.0 20.0 20.0(n) Anti-yellowing 20.0 20.0 20.0 20.0 additive (o) Amine Catalyst 3.73.7 3.7 3.7 (p)

[0129] The ingredients listed in Table 2 were pre-blended in a Hensheldry blender for 30 to 60 seconds. The pre-blends were then melt-blendedin a Werner & Pfleider co-rotating twin screw extruder at a screw speedof 450 revolutions per minute to form a molten extrudate having atemperature of 100° C. to 125° C. The molten extrudate was pressed intoa thin sheet, cooled and solidified on a set of chilled stainless stealrollers, broken into smaller chips, milled and classified to formthermosetting clear powder coating compositions having an averageparticle size of from 17 to 27 microns. The clear powder coatingcompositions of Examples 1-4 were applied by electrostatic sprayapplication over test panel substrates, and cured at 145° C. from 30minutes. The test panel substrates had been previously coated with acured black electrocoat primer available from PPG Industries, Inc. asED-5051 electroprimer. The applied powder coating compositions had curedfilm thicknesses of from 66 to 74 microns. The appearance of the powdercoated test panels was evaluated, and the results are summarized inTable 3. TABLE 3 Appearance of Powder Coating Examples 1-4 Example 1Example 2 Example 3 Example 4 20° Gloss 84 84 83 84 Value (q) Longwave1.1 1.5 0.9 1.0 Value (r) Tension 19.2 18.7 19.4 19.2 Value (s)

[0130] The results as summarized in Table 3 shows that thermosettingpowder coating compositions according to the present invention, i.e.,Examples 2, 3 and 4, provide coatings having appearance that is similarto that of coatings obtained from comparative compositions, i.e.,Example 1. In addition, the powder coating compositions of Examples 2, 3and 4 were observed to have good room temperature physical stability,i.e., they remained free flowing and showed no sings of sintering orclumping after 24 hours. However, the comparative powder coatingcomposition of Example 1 was observed to have very poor room temperaturephysical stability (becoming sintered, clumped and nearly solid in lessthan 24 hours).

[0131] The present invention has been described with reference tospecific details of particular embodiments thereof. It is not intendedthat such details be regarded as limitations upon the scope of theinvention except insofar as and to the extent that they are included inthe accompanying claims.

We claim:
 1. A thermosetting composition comprising a co-reactable solid, particulate mixture of: (a) epoxy functional polymer prepared by atom transfer radical polymerization initiated in the presence of an initiator having at least one radically transferable group, and in which said epoxy functional polymer contains at least one of the following polymer chain structures: -[(M)_(p)-(G)_(q)]_(x)- and -[(G)_(q)-(M)_(p)]_(x)- wherein M is a residue, that is free of oxirane functionality, of at least one ethylenically unsaturated radically polymerizable monomer; G is a residue, that has oxirane functionality, of at least one ethylenically unsaturated radically polymerizable monomer; p and q represent average numbers of residues occurring in a block of residues in each polymer chain structure; and p, q and x are each individually selected for each structure such that said epoxy functional polymer has a number average molecular weight of at least 250; and (b) co-reactant having functional groups reactive with the epoxy groups of (a).
 2. The composition of claim 1 wherein said co-reactant is a carboxylic acid functional co-reactant containing from 4 to 20 carbon atoms.
 3. The composition of claim 2 wherein said carboxylic acid functional co-reactant is selected from the group consisting of dodecanedioic acid, azelaic acid, adipic acid, 1,6-hexanedioic acid, succinic acid, pimelic acid, sebasic acid, maleic acid, citric acid, itaconic acid, aconitic acid and mixtures thereof.
 4. The composition of claim 1 wherein said co-reactant is represented by the following general formula:

wherein R is the residue of a polyol, E is a divalent linking group having from 2 to 10 carbon atoms, and n is an integer of from 2 to
 10. 5. The composition of claim 4 wherein said polyol from which R is derived is selected from the group consisting of ethylene glycol, di(ethylene glycol), trimethylolethane, trimethylolpropane, pentaerythritol, di-trimethylolpropane and di-pentaerythritol; E is selected from the group consisting of 1,2-cyclohexylene and 4-methyl-1,2-cyclohexylene; and n is an integer of from 2 to
 6. 6. The composition of claim 1 wherein said epoxy functional polymer is selected from the group consisting of linear polymers, branched polymers, hyperbranched polymers, star polymers, graft polymers and mixtures thereof.
 7. The composition of claim 1 wherein said epoxy functional polymer has a number average molecular weight of from 500 to 16,000, and a polydispersity index of less than 2.0.
 8. The composition of claim 1 wherein said initiator is selected from the group consisting of linear or branched aliphatic compounds, cycloaliphatic compounds, aromatic compounds, polycyclic aromatic compounds, heterocyclic compounds, sulfonyl compounds, sulfenyl compounds, esters of carboxylic acids, polymeric compounds and mixtures thereof, each having at least one radically transferable halide.
 9. The composition of claim 8 wherein said initiator is selected from the group consisting of halomethane, methylenedihalide, haloform, carbon tetrahalide, 1-halo-2,3-epoxypropane, methanesulfonyl halide, p-toluenesulfonyl halide, methanesulfenyl halide, p-toluenesulfenyl halide, 1-phenylethyl halide, C₁-C₆-alkyl ester of 2-halo-C₁-C₆-carboxylic acid, p-halomethylstyrene, mono-hexakis(α-halo-C₁-C₆-alkyl)benzene, diethyl-2-halo-2-methyl malonate, ethyl 2-bromoisobutyrate and mixtures thereof.
 10. The composition of claim 1 wherein said epoxy functional polymer has an epoxy equivalent weight of from 128 to 10,000 grams/equivalent.
 11. The composition of claim 1 wherein M is derived from at least one of vinyl monomers, allylic monomers and olefins.
 12. The composition of claim 11 wherein M is derived from at least one of alkyl (meth)acrylates having from 1 to 20 carbon atoms in the alkyl group, vinyl aromatic monomers, vinyl halides, vinyl esters of carboxylic acids and olefins, and G is derived from at least one of glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl(meth)acrylate, 2-(3,4-epoxycyclohexyl)ethyl(meth)acrylate and allyl glycidyl ether.
 13. The composition of claim 1 wherein said epoxy functional polymer has at least one of the following polymer chain structures: φ-[[(M)_(p)-(G)_(q)]_(x)-(M)_(r)-T]_(z) and φ-[[(G)_(q)-(M)_(p)]_(x)-(G)_(s)-T]_(z) wherein φ is or is derived from the residue of said initiator free of said radically transferable group; T is or is derived from said radically transferable group of said initiator; x is independently from 1 to 100 for each structure; p and q are each independently within the range of 0 to 100 for each x-segment and for each structure, the sum of p and q being at least 1 for each x-segment, and q being at least 1 for at least one x-segment; r and s are each independently for each structure within the range of 0 to 100; z is independently for each structure at least 1; and said epoxy functional polymer has a polydispersity index of less than 2.0.
 14. The composition of claim 13 wherein said epoxy functional polymer has a number average molecular weight of from 500 to 16,000, and a polydispersity index of less than 1.8.
 15. The composition of claim 13 wherein p is independently selected for each structure within the range of 1 to 20; and q is independently selected for each structure within in the range of 1 to
 20. 16. The composition of claim 13 wherein x is independently selected for each structure within the range of 1 to
 50. 17. The composition of claim 15 wherein T is halide.
 18. The composition of claim 17 wherein T is derived from a dehalogenation post-reaction.
 19. The composition of claim 18 wherein said dehalogenation post-reaction comprises contacting said epoxy functional polymer with a limited radically polymerizable ethylenically unsaturated compound.
 20. The composition of claim 19 wherein said limited radically polymerizable ethylenically unsaturated compound is selected from the group consisting of 1,1-dimethylethylene, 1,1-diphenylethylene, isopropenyl acetate, alpha-methyl styrene, 1,1-dialkoxy olefin and combinations thereof.
 21. The composition of claim 1 wherein the equivalent ratio of epoxy equivalents in said epoxy functional polymer (a) to the equivalents of reactive functional groups in said co-reactant (b) is from 0.5:1 to 2:1.
 22. The composition of claim 1 wherein said epoxy functional polymer (a) is present in said thermosetting composition in amounts of from 50 to 90 percent by weight, based on total resin solids weight, and said co-reactant (b) is present in said thermosetting composition in amounts of from 10 to 50 percent by weight, based on total resin solids weight.
 23. A method of coating a substrate comprising: (a) applying to said substrate a thermosetting composition; (b) coalescing said thermosetting composition to form a substantially continuous film; and (c) curing said thermosetting composition by the application of heat, wherein said thermosetting composition comprises a co-reactable solid, particulate mixture of: (i) epoxy functional polymer prepared by atom transfer radical polymerization initiated in the presence of an initiator having at least one radically transferable group, and in which said epoxy functional polymer contains at least one of the following polymer chain structures: -[(M)_(p)-(G)_(q)]_(x)- and -[(G)_(q)-(M)_(p)]_(x)- wherein M is a residue, that is free of oxirane functionality, of at least one ethylenically unsaturated radically polymerizable monomer; G is a residue, that has oxirane functionality, of at least one ethylenically unsaturated radically polymerizable monomer; p and q represent average numbers of residues occurring in a block of residues in each polymer chain structure; and p, q and x are each individually selected for each structure such that said epoxy functional polymer has a number average molecular weight of at least 250; and (ii) co-reactant having functional groups reactive with the epoxy groups of (i).
 24. The method of claim 23 wherein said co-reactant is a carboxylic acid functional co-reactant containing from 4 to 20 carbon atoms.
 25. The method of claim 24 wherein said carboxylic acid functional co-reactant is selected from the group consisting of dodecanedioic acid, azelaic acid, adipic acid, 1,6-hexanedioic acid, succinic acid, pimelic acid, sebasic acid, maleic acid, citric acid, itaconic acid, aconitic acid and mixtures thereof.
 26. The method of claim 23 wherein said co-reactant is represented by the following general formula:

wherein R is the residue of a polyol, E is a divalent linking group having from 2 to 10 carbon atoms, and n is an integer of from 2 to
 10. 27. The method of claim 26 wherein said polyol from which R is derived is selected from the group consisting of ethylene glycol, di(ethylene glycol), trimethylolethane, trimethylolpropane, pentaerythritol, di-trimethylolpropane and di-pentaerythritol; E is selected from the group consisting of 1,2-cyclohexylene and 4-methyl-1,2-cyclohexylene; and n is an integer of from 2 to
 6. 28. The method of claim 23 wherein said epoxy functional polymer is selected from the group consisting of linear polymers, branched polymers, hyperbranched polymers, star polymers, graft polymers and mixtures thereof.
 29. The method of claim 23 wherein said epoxy functional polymer has a number average molecular weight of from 500 to 16,000, and a polydispersity index of less than 2.0.
 30. The method of claim 23 wherein said initiator is selected from the group consisting of linear or branched aliphatic compounds, cycloaliphatic compounds, aromatic compounds, polycyclic aromatic compounds, heterocyclic compounds, sulfonyl compounds, sulfenyl compounds, esters of carboxylic acids, polymeric compounds and mixtures thereof, each having at least one radically transferable halide.
 31. The method of claim 30 wherein said initiator is selected from the group consisting of halomethane, methylenedihalide, haloform, carbon tetrahalide, 1-halo-2,3-epoxypropane, methanesulfonyl halide, p-toluenesulfonyl halide, methanesulfenyl halide, p-toluenesulfenyl halide, 1-phenylethyl halide, C₁-C₆-alkyl ester of 2-halo-C₁-C₆-carboxylic acid, p-halomethylstyrene, mono-hexakis (α-halo-C₁-C₆-alkyl)benzene, diethyl-2-halo-2-methyl malonate, ethyl 2-bromoisobutyrate and mixtures thereof.
 32. The method of claim 23 wherein said epoxy functional polymer has an epoxy equivalent weight of from 128 to 10,000 grams/equivalent.
 33. The method of claim 23 wherein M is derived from at least one of vinyl monomers, allylic monomers and olefins.
 34. The method of claim 33 wherein M is derived from at least one of alkyl (meth)acrylates having from 1 to 20 carbon atoms in the alkyl group, vinyl aromatic monomers, vinyl halides, vinyl esters of carboxylic acids and olefins, and G is derived from at least one of glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl(meth)acrylate, 2-(3,4-epoxycyclohexyl)ethyl(meth)acrylate and allyl glycidyl ether.
 35. The method of claim 23 wherein said epoxy functional polymer has at least one of the following polymer chain structures: φ-[[(M)_(p)-(G)_(q)]_(x)-(M)_(r)-T]_(z) and φ-[[(G)_(q)-(M)_(p)]_(x)-(G)_(s)-T]_(z) wherein φ is or is derived from the residue of said initiator free of said radically transferable group; T is or is derived from said radically transferable group of said initiator; x is independently from 1 to 100 for each structure; p and q are each independently within the range of 0 to 100 for each x-segment and for each structure, the sum of p and q being at least 1 for each x-segment, and q being at least 1 for at least one x-segment; r and s are each independently for each structure within the range of 0 to 100; z is independently for each structure at least 1; and said epoxy functional polymer has a polydispersity index of less than 2.0.
 36. The method of claim 35 wherein said epoxy functional polymer has a number average molecular weight of from 500 to 16,000, and a polydispersity index of less than 1.8.
 37. The method of claim 35 wherein p is independently selected for each structure within the range of 1 to 20; and q is independently selected for each structure within in the range of 1 to
 20. 38. The method of claim 35 wherein x is independently selected for each structure within the range of 1 to
 50. 39. The method of claim 35 wherein T is halide.
 40. The method of claim 39 wherein T is derived from a dehalogenation post-reaction.
 41. The method of claim 40 wherein said dehalogenation post-reaction comprises contacting said epoxy functional polymer with a limited radically polymerizable ethylenically unsaturated compound.
 42. The method of claim 41 wherein said limited radically polymerizable ethylenically unsaturated compound is selected from the group consisting of 1,1-dimethylethylene, 1,1-diphenylethylene, isopropenyl acetate, alpha-methyl styrene, 1,1-dialkoxy olefin and combinations thereof.
 43. The method of claim 23 wherein the equivalent ratio of epoxy equivalents in said epoxy functional polymer (i) to the equivalents of reactive functional groups in said co-reactant (ii) is from 0.5:1 to 2:1.
 44. The method of claim 23 wherein said epoxy functional polymer (i) is present in said thermosetting composition in amounts of from 50 to 90 percent by weight, based on total resin solids weight, and said co-reactant (ii) is present in said thermosetting composition in amounts of from 10 to 50 percent by weight, based on total resin solids weight.
 45. A substrate coated by the method of claim
 23. 46. A multi-component composite coating composition comprising: (a) a base coat deposited from a pigmented film-forming composition; and (b) a transparent top coat applied over said base coat, wherein said transparent top coat is deposited from a clear film-forming thermosetting composition comprising a co-reactable solid, particulate mixture of: (i) epoxy functional polymer prepared by atom transfer radical polymerization initiated in the presence of an initiator having at least one radically transferable group, and in which said epoxy functional polymer contains at least one of the following polymer chain structures: -[(M)_(p)-(G)_(q)]_(x)- and -[(G)_(q)-(M)_(p)]_(x)- wherein M is a residue, that is free of oxirane functionality, of at least one ethylenically unsaturated radically polymerizable monomer; G is a residue, that has oxirane functionality, of at least one ethylenically unsaturated radically polymerizable monomer; p and q represent average numbers of residues occurring in a block of residues in each polymer chain structure; and p, q and x are each individually selected for each structure such that said epoxy functional polymer has a number average molecular weight of at least 250; and (ii) co-reactant having functional groups reactive with the epoxy groups of (i).
 47. The multi-component composite coating composition of claim 46 wherein said co-reactant is a carboxylic acid functional co-reactant containing from 4 to 20 carbon atoms.
 48. The multi-component composite coating composition of claim 47 wherein said carboxylic acid functional co-reactant is selected from the group consisting of dodecanedioic acid, azelaic acid, adipic acid, 1,6-hexanedioic acid, succinic acid, pimelic acid, sebasic acid, maleic acid, citric acid, itaconic acid, aconitic acid and mixtures thereof.
 49. The multi-component composite coating composition of claim 46 wherein said co-reactant is represented by the following general formula:

wherein R is the residue of a polyol, E is a divalent linking group having from 2 to 10 carbon atoms, and n is an integer of from 2 to
 10. 50. The multi-component composite coating composition of claim 49 wherein said polyol from which R is derived is selected from the group consisting of ethylene glycol, di(ethylene glycol), trimethylolethane, trimethylolpropane, pentaerythritol, di-trimethylolpropane and di-pentaerythritol; E is selected from the group consisting of 1,2-cyclohexylene and 4-methyl-1,2-cyclohexylene; and n is an integer of from 2 to
 6. 51. The multi-component composite coating composition of claim 46 wherein said epoxy functional polymer is selected from the group consisting of linear polymers, branched polymers, hyperbranched polymers, star polymers, graft polymers and mixtures thereof.
 52. The multi-component composite coating composition of claim 46 wherein said epoxy functional polymer has a number average molecular weight of from 500 to 16,000, and a polydispersity index of less than 2.0.
 53. The multi-component composite coating composition of claim 46 wherein said initiator is selected from the group consisting of linear or branched aliphatic compounds, cycloaliphatic compounds, aromatic compounds, polycyclic aromatic compounds, heterocyclic compounds, sulfonyl compounds, sulfenyl compounds, esters of carboxylic acids, polymeric compounds and mixtures thereof, each having at least one radically transferable halide.
 54. The multi-component composite coating composition of claim 53 wherein said initiator is selected from the group consisting of halomethane, methylenedihalide, haloform, carbon tetrahalide, 1-halo-2,3-epoxypropane, methanesulfonyl halide, p-toluenesulfonyl halide, methanesulfenyl halide, p-toluenesulfenyl halide, 1-phenylethyl halide, C₁-C₆-alkyl ester of 2-halo-C₁-C₆-carboxylic acid, p-halomethylstyrene, mono-hexakis(α-halo-C₁-C₆-alkyl)benzene, diethyl-2-halo-2-methyl malonate, ethyl 2-bromoisobutyrate and mixtures thereof.
 55. The multi-component composite coating composition of claim 46 wherein said epoxy functional polymer has an epoxy equivalent weight of from 128 to 10,000 grams/equivalent.
 56. The multi-component composite coating composition of claim 46 wherein M is derived from at least one of vinyl monomers, allylic monomers and olefins.
 57. The multi-component composite coating composition of claim 56 wherein M is derived from at least one of alkyl (meth)acrylates having from 1 to 20 carbon atoms in the alkyl group, vinyl aromatic monomers, vinyl halides, vinyl esters of carboxylic acids and olefins, and G is derived from at least one of glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl(meth)acrylate, 2-(3,4-epoxycyclohexyl)ethyl(meth)acrylate and allyl glycidyl ether.
 58. The multi-component composite coating composition of claim 46 wherein said epoxy functional polymer has at least one of the following polymer chain structures: φ-[[(M)_(p)-(G)_(q)]_(x)-(M)_(r)-T]_(z) and φ-[[(G)_(q)-(M)_(p)]_(x)-(G)_(s)-T]_(z) wherein φ is or is derived from the residue of said initiator free of said radically transferable group; T is or is derived from said radically transferable group of said initiator; x is independently from 1 to 100 for each structure; p and q are each independently within the range of 0 to 100 for each x-segment and for each structure, the sum of p and q being at least 1 for each x-segment, and q being at least 1 for at least one x-segment; r and s are each independently for each structure within the range of 0 to 100; z is independently for each structure at least 1; and said epoxy functional polymer has a polydispersity index of less than 2.0.
 59. The multi-component composite coating composition of claim 58 wherein said epoxy functional polymer has a number average molecular weight of from 500 to 16,000, and a polydispersity index of less than 1.8.
 60. The multi-component composite coating composition of claim 58 wherein p is independently selected for each structure within the range of 1 to 20; and q is independently selected for each structure within in the range of 1 to
 20. 61. The multi-component composite coating composition of claim 58 wherein x is independently selected for each structure within the range of 1 to
 50. 62. The multi-component composite coating composition of claim 58 wherein T is halide.
 63. The multi-component composite coating composition of claim 62 wherein T is derived from a dehalogenation post-reaction.
 64. The multi-component composite coating composition of claim 63 wherein said dehalogenation post-reaction comprises contacting said epoxy functional polymer with a limited radically polymerizable ethylenically unsaturated compound.
 65. The multi-component composite coating composition of claim 64 wherein said limited radically polymerizable ethylenically unsaturated compound is selected from the group consisting of 1,1-dimethylethylene, 1,1-diphenylethylene, isopropenyl acetate, alpha-methyl styrene, 1,1-dialkoxy olefin and combinations thereof.
 66. The multi-component composite coating composition of claim 46 wherein the equivalent ratio of epoxy equivalents in said epoxy functional polymer (i) to the equivalents of reactive functional groups in said co-reactant (ii) is from 0.5:1 to 2:1.
 67. The multi-component composite coating composition of claim 46 wherein said epoxy functional polymer (i) is present in said clear film-forming thermosetting composition in amounts of from 50 to 90 percent by weight, based on total resin solids weight, and said co-reactant (ii) is present in said clear film-forming thermosetting composition in amounts of from 10 to 50 percent by weight, based on total resin solids weight.
 68. A substrate having said multi-component composite coating composition of claim 46 deposited thereon.
 69. A substrate having said multi-component composite coating composition of claim 58 deposited thereon. 